1. Field of the Invention
This invention relates to industrial lighting and, more particularly, to high-output lighting fixtures using fluorescent lighting sources.
2. Background Information
High-output lighting fixtures are used in a variety of indoor and outdoor applications. Notably, a large unobstructed volume, such as a warehouse or indoor arena may employ a significant number of fixtures, which depend from the roof or supporting beams at predetermined spacing, in order to create a desired lighting effect. The fixtures often used for this purpose are metal-halide bulb fixtures, such as the exemplary fixture 100 shown in FIG. 1. Such metal-halide fixtures typically include a base 102 attached to one end of a chain or cable 104, with the chain's opposing end (not shown) secured to the building's roof or an associated support beam. The exemplary fixture base 102 includes a mounting socket 106 for a single large metal-halide bulb 110. This type of fixture may mount another high-output single bulb (rather than metal-halide) including a mercury vapor bulb or sodium bulb. Typically, the bulb 110 is encased within an open space 112 defined by a hemispherical (or other shape) shield or shade 114, having a lower end 120 that is open to allow light to escape. The inner surface 122 of the field may be reflective or transparent, depending upon the application. In general, the shape of the shield or shade 114 is designed to reflect the light generated by the bulb in a desired pattern onto the floor below.
Metal-halide, and similar types of single-bulb fixtures, exhibit certain performance characteristics. For example, they tend to have a relatively wide light distribution that, because of the fixed shade and single source, is not variable or directable. These bulbs also tend to create spots of light on the ground surface while areas between the fixture light spots may be darker. This leads to the so-called “cave effect.” These lighting performance characteristics may, thus, provide a less-desirable lit space on which to conduct activities. In addition, metal-halide and other high-output bulbs or sources tend to generate substantial waste heat. This increases is a result of inefficiency in converting electric power to light, and where a large number of fixtures are employed, may actually serve as a significant heat source in the building volume (such heat increasing overall cooling costs and being particularly problematic in a cool environment such as an ice arena). Also, the excessive heat may eventually degrade the materials from which the fixture is constructed.
Furthermore, metal-halide bulbs or sources tend to exhibit weakened output after approximately one month of use. This leads to even lower efficiencies and even higher electric consumption for such fixtures. In addition, metal-halide bulbs require substantial warm-up time to attain full brightness. Again, this increases consumption by requiring lights to be activated a significant time before they are actually needed and/or is otherwise inconvenient, as lights are not available on demand.
Finally, metal-halide bulbs, and other commercial, high-output incandescent light sources are plagued with significant color rendition problems. In essence, their output often exhibits a monotone/monochromatic color that washes out the target area in an “unnatural” hue. For example, a heavy orange or yellow tint may be present. In most instances a fuller-spectrum of light is highly desired.
It is therefore desirable to provide a light fixture that eliminates or reduces some or all of the disadvantages of metal-halide fixtures and those using similar bulb or source technologies.